In such a separation type air conditioner, in order to allow the entire air conditioner to perform an optimal operation, it is necessary to transmit information by performing two-way communication between a control device of the indoor unit and a control device of an outdoor unit. For example, commands of an operation request, a change in set temperature, a timer, a change in operation mode, or a stop request, which are input by a user via a remote controller, an indoor temperature output from a temperature detection circuit or the like, an ON/OFF command of a refrigerant compressor of the outdoor unit, and the like are sent from the control device of the indoor unit to the control device of the outdoor unit.
In addition, a rotating speed of a refrigerant compressor of the outdoor unit, failure information of the outdoor unit, outdoor temperature information, and the like are sent from the control device of the outdoor unit to the control device of the indoor unit. In addition, each of the control devices is controlled to be integrally operated by exchanging control information signals, such as a signal about an operation condition or a set temperature.
Such an air conditioner is suggested in Japanese laid-open No. 2005-61676 (PTL 1) or the like, but is also suggested in many other PTLs or the like. However, as the above-described method of transmitting the control information signal, a method of transmitting a signal pulse which is a transmission signal at a predetermined frequency by connecting the control devices of the outdoor unit and the indoor unit to each other by a dedicated signal line, is known. In addition to this, a method of transmitting information by using an AC current of a power line which supplies power to the control devices of the outdoor unit and the indoor unit, is also known.
In general, as communication means of each of the control devices of the outdoor unit and the indoor unit of the air conditioner, at least two communication means having different communication speeds are mainly used, and in the related art, as a switching method of the communication speed, switching is performed by using a manual changeover switch. For example, the manual changeover switch is provided in the control device of the outdoor unit or the control device of the indoor unit, or in the control devices of the outdoor unit and the indoor unit, and the communication means is selected by switching each of the manual changeover switches in accordance with a communication speed selected by an installation worker of the air conditioner.